Rotala rotundifolia (roundleaf toothcup) care

Light

Bright but filtered. Rotala rotundifolia burns within days in unfiltered south-facing summer sun, and stops growing within months in deep shade. Submerged plant that grows green in moderate aquarium light but turns pink-to-red and grows compact under high LED output (roughly 40-70+ PAR). Higher light plus lean nitrate intensifies the colour. If you only have a south window, set the plant back 1.5 m or hang a sheer curtain — both knock the intensity down into the right range.

Watering

Watering rotala rotundifolia: submerged permanently; 30-50% aquarium water changes weekly. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. Lives underwater in freshwater. Adaptable across soft to hard water (3-15 dGH), pH 6.0-7.5. Grows without CO2 but is denser and more colourful with injection (15-30 ppm).

Soil and pot

Rotala rotundifolia grows best in aquarium gravel or aquasoil substrate. Roots readily in fine gravel, sand or nutrient aquasoil. It feeds heavily from the water column, so a fertile substrate is helpful but not essential. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Rotala rotundifolia sits happiest at around 100% (submerged aquatic) humidity and 18-28°C (64-82°F). Grown fully underwater, so ambient humidity does not apply. It also grows emersed in humid wabi-kusa or pond margins, where leaves become rounder and CO2 from air is used instead. If you keep the room above 18 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed rotala rotundifolia sparingly. Dose a balanced liquid aquarium fertiliser with nitrate, phosphate, potassium and trace elements; iron supports red tones. It is a fast grower, so regular water-column dosing prevents deficiency in planted tanks. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on rotala rotundifolia in the Growli community. Each is annotated with the most common cause so you know where to start.

• Stays green instead of pink/red — Colour is light-driven. Increase PAR and keep nitrate slightly lean; without high light it grows healthy but plain green.
• Leggy stems with bare lower halves — Too little light or shading from above causes lower leaves to drop. Increase light, thin the canopy, and replant trimmed tops.
• Tip stunting — Often a micronutrient or unstable-CO2 issue. Maintain steady CO2 and dose trace elements including iron and magnesium.
• Overgrowth and crowding — Its speed means it quickly fills the tank and shades neighbours. Trim weekly and remove excess stems to keep the aquascape balanced.

Propagation

Trim the top 5-10 cm of a stem and push the cutting into the substrate, where it roots and continues growing; the cut parent stem branches below. Classic cut-and-replant stem propagation. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Rotala rotundifolia is mildly toxic to pets. Rotala is not individually listed by the ASPCA on either the toxic or non-toxic plant lists, so its pet status is unconfirmed. Treat with caution and verify with a vet; as a submerged aquarium plant, ingestion by cats or dogs is unlikely in practice. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Rotala rotundifolia deep-dive guides

Every aspect of rotala rotundifolia care, each with its own calibrated guide:

• Rotala rotundifolia watering schedule
• Rotala rotundifolia light requirements
• Best soil mix for rotala rotundifolia
• Rotala rotundifolia fertilizing guide
• When to repot rotala rotundifolia
• How to propagate rotala rotundifolia
• Rotala rotundifolia growth rate & size
• Rotala rotundifolia cold hardiness
• Rotala rotundifolia temperature & humidity
• Is rotala rotundifolia toxic to cats & dogs?
• Is rotala rotundifolia toxic to cats?
• Is rotala rotundifolia toxic to dogs?

Featured in these plant shortlists

Rotala rotundifolia qualifies for 2 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best plants for a north-facing window — Houseplants for a north-facing window: bright, even, indirect light and no scorching direct sun. Each pick verified against its documented light needs.
• Best fast-growing houseplants — Houseplants documented as fast or vigorous growers — quick to fill a pot, cover a pole or trail down a shelf.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Rotala rotundifolia is also commonly called roundleaf toothcup or pink Rotala.

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